Propeller blade



Oct. 14, 1947. G. w. HARDY PROPELLER BLADE Filed June 16, 1945 my!! Z4 Haj/8,5 2

7 l ff I j f M7 INVENToR 6 B'Y GORDON W HARDY y ff f-wf@ ATTORNEY Patented Oct. 14, H1947 PROPELLER BLADE.

Gordon W. Hardy, Cleveland Heights, Ohio, assgnor to The Marquette Metal Products Company, Cleveland, Ohio, a corporation of Ohio ApplicationJune 16, 1943, Serial No. 491,038

This invention relates to a propeller blade particularly for aircraft and a new method of making such blade.

One object of the invention is to provide a propeller blade which can be made without any great amount of hand work and have strength, flexibility and other desirable. characteristics comparable to, if not excelling, the higher grades of laminated wooden propellers and all-metal propellers while at the same time being moisture and impact resistant and of. light Weight.

A further object is to provide an improved method of making metallically armored propeller blades.

A specic object is to provide a propeller blade having an adequately reinforced core including high strength plastic material and an armor sheath partially or wholly covering the same of sufcient tensile strength and impact resistance to prevent chipping andabrading of the propeller surface as by projectiles, particularly at low tem--A peratures.

A further object is to provide a composite propeller blade with. imperforate metallicV armor, wherein the armor is of pre-formed sheet metal and core portions of the blade comprise plastic material of tough and` strongcharacter sofassociated with the armor that all parts, of. the armor are iirmly and solidlybuttressed orbacked by the core material notwithstanding any inherent tendency that may existfor themetal to `become loosened locally or otherwise4 from said core material. Y

Another object is to provide an improvedmanner of making, fromsheet metal parts, an armoring shell for a propeller blade having. an inter-nal reinforcing and shape-sustainingY structure,

which armoring shell iscapable of being made accurately to size and shape and asv strong as though made from one piece of sheet metal.

A further object4 is to provide a novel and effective manner of `incorporating plastic material with a sheet metal shell such, for example, asr

referred to in the next preceding object so as to produce a propeller blade having marked strength, distortion and bending resistance and other desirable characteristics.

Another object is to provide an improvedpropeller blade made partially from plastic material with an improved reinforcing core formed sub-` stantially as an integral part of a shank piece or butt of the blade suitable for mounting in a metal hub provided with means for turning the blade about its longitudinal axis for pitch adjustment, feathering and the like'.

3 Claims. (Cl. 170--159) Another object is to provide a de-icing means for propeller blades which means is operative eliciently to de-ice all the blade surfaces on which ice is likely t0 accumulate.

Further objects include the provision of a pro-` peller blade having adequate tensile, compressive, twist resisting and impact resisting strength, notwithstanding relatively light weight and resistance to the effects of temperature change and relative humidity or even immersion in water for long periods.

Further objects and features of the invention will become apparent from the following description and by reference to the accompanying drawings, in which Fig. 1 is a front view of one blade of a propeller, partly in central section, and a more or less diagrammatic representation of a hub on which the blade may be mounted;v

Fig. 2 is an exploded typical cross-sectional view showing two sheet metal parts or assemblies preparatory to assembling them in accordance herewith to produce a pre-formed hollow shell approx'mately of propeller blade form;

Fig. 3 is a typical cross sectional detail view showing one manner of eifecting a strong joint between sheet metal parts in forming a shell of propeller blade shape;

Fig. 4 is a typical cross sectional view showing two forming dies by which the final blade shape may be determined and effected and molding pressure'applied to an organic plastic component of the blade;

Fig. 5 is a typical transverse cross sectional view of the completed blade;

Fig. 6 is an assembly view of a propeller-blade shell and an associated supporting die, said view showing a variation of the preferred method of forming the blade and also variations in the blade construction;

Fig. 'l is a relatively enlarged longitudinal sectional view of shank portions, of a blade made according to Fig. 6 after a plastic component therefor has been cured or solidified, and

Fig. 8 is a diagram (exploded view) showing a further variation ofthe essential method and blade construction produced hereby.

This application and my application Serial No. 491,037 iiled concurrently herewith are companion cases both showing methods of utilizing effectively, in propeller blade construction, cores or core portions of tough, hardenable organic plastic material of high resistance to the various destructive forcesv likely to be imposed on propellers, particularly those designed for use on aircraft. The

plastic in each case is preferably non-resinous material such as cellulose acetate or cellulose acetate butyrate, but other non-brittle materials, both thermoplastic and thermosetting, having similar properties and strength characteristics may be considered equivalents within the intended scope of this invention, A

Prior hereto it has been proposed to use synthetic resins and more or less brittle plastic materials (e. g. hard rubber) as propeller bladeV components and to reinforce said materials in various ways, usually by fabric strips and other embedded members, e. g. paper, wires, etc., so that the synthetic resins and allied materials could serve notwithstanding their inherent brittleness and low tensile strength at normal temperatures; and also it has been proposed to armor such synthetic resins and allied materials with doped tape and with partial or complete envelopes of metal to resist the tendency for the inherently brittle materials to be chipped or shattered upon impact with sand, stones, llak and missiles generally. The great difference in thermal expansion and contraction between such previously proposed plastic materials as mentioned and metals as well as the inherent brittleness and lack of tensile strength of the plastics has, I believe, prevented the general adoption of composite plastic and metal propeller -blades by the airplane industry to date hereof. As indicated. by the foregoing objects of the present invention the latter offers a better solution to the various problems encountered in composite airplane propeller construction as will become apparent from the following description of the preferred forms and process or method steps, and produces propeller blades superior in many respects to all metal and laminated wooden propellers, with and without protective metallic armor, and at relatively low cost.

Referring further to the drawing, Fig. 1 shows a left hand portion of a blade in central section and a right hand portion in elevation. The blade has a shank or butt portion I suitably formed, for example, generally cylindrically, and with flange projections as at 2 which, in the form shown, are buttress thread effects for mounting the propeller in a suitable hub. A hub is diagrammatically indicated at 3 with a tubular extension 4 adapted to receive the projections 2 and which may include provision for turning the entire blade about its longitudinal axis into high and -low pitch, feathering and/or reverse positions. Reference is directed to my copending apolication, Serial No. 498,492, filed August 13, 1943, for a suitable hub construction providing for variable pitch as to the blades of which there may be any suitable number and arrangement and for one manner of supplying de-icing-fluid to the blades. The ribs 2 on the butt portion I are, in actual practice, supported in split mounting sleeve members such as shown for example in my copending application Serial No. 476,398, filed February 19, 1943. For simplicity, the butt portion I, as herein shown, is embraced by metal of the associated hub extension Il as though turnable for pitch adjustment therein.

The principal portion of the body of the propeller blade is plastic material on the order of that mentioned above, namely cellulose acetate or cellulose acetate butyrate or materials of equivalent desired properties (see Plastics Catalogue 1942 for example). The plastic is preferably molded about an extension of the butt or shank piece I constituting a blade reinforce bar indienr 4 cated at 5 and which is generally tapered toward the tip portion of the blade partly to reduce the tendency for the metal of the bar to crystallize during flexure of the blade in use, or in other words, in order to lend greater rigidity to portions of the blade nearer the hub than to portions toward the tip. Also, preferably, the plastic is molded about a metal reinforcing sheet or plate I0, which is rigidly attached to the reinforce bar 5 at a central longitudinal slot of the bar 5, e. g. in the manner explained more fully in said companion case.

The sheet or plate I0 has projections at each side formed as by the provision of a fairly large number of openings as at II and flanges around the openings projecting outwardly at respective sides of the principal plane of the sheet or plate I0 as suggested for example in Fig. 5 at 12. The exterior surfaces of the completed blade are formed by a metal shell I5 comprising for example two peripherally matching sheet metal sections IB and Il, typical section portions of which are as shown in Fig, 2. The section I6 forms the camber side of the blade and I 'l the thrust side.

The preferred manner of forming the shell I5 so that the shell, together with the shank or butt piece I and reinforce bar 5, if used, may constitute a'mold for the plastic material in forming the same to propeller blade shape is as shown by Figs. 2 and 3. Each shell preferably has adjacent the leading I la, respectively, a generally triangular strip of ymaterial I8 brazed or otherwise secured thereto on the inside of the shell so that, in effect, the edges of the metal of the respective shells are amplified-made wider-for facilitating the formation of permanent strong joints between the aligned edge portions of the shells. The particular form of the strips I8, which may be modified, is mainly in order that the plastic body (to be described later) will more effectively interlock the shells together at the brazed or welded joints. The trailing edge portions I 6b and I 'Ib of the two shells are similarly supplied with joint-surfaceenlarging and plastic-interlocking strips I9 also shown as generally triangular in section.

It will be observed that the strips I8 and I9 ywhen of triangular section or other shape providing opposite relatively diverging and inwardly extending surfaces are nely held together or interlocked with the solidified plastic (see P', Fig. 5) so that the plastic effects an auxiliary or insuring bond between the shell edges in cases where the brazing or welding may be carelessly done.

Instead of using separate strips such as I 8, the matching edges of the two shell sections I6 and I'I may be flanged inwardly in the manner suggested, for example, by Fig. 8 hereof to be described later. in which event the inwardly directed flanges are locked together by the plastic body adjacent the joint between the shell sections, regardless of the shapes of such flanges and further interlocked if the flanges are of appropriate shape.

While the two shell sections equipped with the strips I8 and I 9 (or flanged for similar edgesurface-amplifying effect) can be secured together by any known welding method, I preferably braze the shell sections together by interpositioning between the registering edge surfaces fairly thin and preferably peripherally continuous welding stock as suggested at 20, for eX- ample brass or other readily fused metal. The welding stock as well as the strips I8 and I9 run continuously around the blade shell sections from edge portions I 5a and I apolnt-adjacentothe open end' of. thefcompl'etedr shell. around tbevtip: and back. to a. similar; point. adjacent" theV open endbut on the opposite side from the rst mentioned: point` Prior toassembling-"t'he-.two shell sections i6.. and I1. togethergflanged strips suchas 2.2rand 23 are secured as bywelding to theinsidcsuriaces. ofj they shells andv running. substantially;r for. their entire length so that i the.- portionsy of. thee shells;= intermediate. the.. brazed or; welded. edges. above.: described will be solidly;l interloclied witlfrE and@ backed or buttrf-:ssedY byy thelplastic material to: bef-later contained inthe completed shellv I5. As. shown each of thestrips, 22J and 23 has two; aneeatheanges .all being indicatedlat. 24;. The:y flanges of.' each. stripf divergev ini thepar-ticnlarformillustrated .for dovetailfinterloclc eifect'withV the plastic. Buttons: withTs-heads. can bevusedi instead ofstripsr- Theremay, of course; be.` provided aa greater number of strips suchas 22rand 23onfeach=side Y wall depending upon the tendency for the metalV ofY the side wallsatodraw awayifrom the solidied plastic. The variationwouldrresult-l from' the..y use@ ofdifferent metals=toforrn the shell sections.

The shelksection- I6 which .f constitutes the cam-- berf-surface-formingelement. ofTv the blade has. secured thereto insidefnear. the-leadinggedge' a. metaltuhel fon containing and conveying; deicing; fluid to. theV bladel surfaces which arellikelyto accumulateice. The tube 25 may. extend through the buttv piece lat a suitable eccentricl boreftherein for connection. as at. 261 with ai rcspective flexible conduit 21 leading to a source.'- ofv supply of' deficing'; huid-such asl alcohol; The arrangement, shown: in.- depending application, SeriallNor 4985492L1i1ed- August 13111943, enf ablesl all;- ofy the blades'.` to 1 be supplied simultanea' ously wit-h duid from a single sourcefsuch as` a.,-

central tube-28v (diagrammatic) andgthe flexible connections permit' the shank or buttvv piecesy of. the blades to turn in` their mountingsas wouldbe necessary in the event. the blades arefusedzfor variable pitch during ilight. The bladeY has a plurality of small. openings asat 30, which are. drilled throughI from theV outside of. the bladev into'thetube 25 to carry. the delicer fluid tosthe blade. surfaces.l would be such a seriesof openings 3D. asrindi cated o n Fig. 1 for'the camber side oftheblade The preferredI arrangement edges ci the.1sliells.-` andistrips.A I8 and lilareiny tegralh'fT joined: together through the interme-v diaryrofthefused welding stock 2G.' 'IT-he welding( stoclrcanroffcoursei take other forms.y In cases where the4 shell. stockiisfairly.- thick, it is. not necessaryv to. extend the surfaceas by application ofthe. strips I 8; andV I 9 Aiterthe tubular shell I5.has been fully formed asdescribed abovethe open end portion of the shellradjacent thehub maybe extended as from thepoint indicatedat 3l'- on Fig. 1` toward the hub. 3 by a.- continuous-or seamless tube 38 of metal=buttbrazed or welded to theV open end of said shell. ory otherwise.A rmly secured thereto,

entirelyv around theY open end of the shell l5..V

A-s' showinv in Figal; the tube.3.8 has a flange 39 the-'lengthiofr the har as desired or found neceser and a lesser number, for example, onethirdas many, leading tothe thrust side of: theblade as. more: fully illustrated and described in my Said` companion. case.` The arrangement is` unique-in.- that. all surfacesalong. the blade from! shank to tip and. which. arelikely toaccumulate. ice are served with de-icerv fluid. The.de.icertube.here..

of is essentiallyA thesame asthat shown by my said companion. case and; somewhat. more fully. explained in that case.

An eicient manner of welding the twoshell. sections I and I1 togetherv is illustrated by Fig .3 whereinsuitable. dies 32. and 32 lightly support thefshells over substantialsurfaces thereof. and. electricalcontactor elements are. arranged in the.Y dies asiat 33.and 3'4- for carrying welding currentV to the shellsv closely adjacent the joints to. be.y formed therebetween. The elements` 33 and 34, preferably comprise strips. oi carbon or. otherV non-arcing conductorV materialwhich. extender tirely about the peripheral portions of the blade. shells. tobe. joined; andY make firmintimate uni form contact therewith to carry the Weldingcur rent, When current of.y opposite-- polarity is apeV plied to: the respectives stripsv of each pair.. the.

sary. The reinforcebar furthermore has a centralrbore. asat 'Iwhich boreextends through thev butt. piece. intoa socket 8 of the latter. Such bore 'l-may beused as an injector passage for in. troducing. the plastic material into the metal assembly as through lateralpassages in the rein.- force bar asiIluStrated. and described inmy said. companion case.

In the present form of blade and method of makingv it I supply-the raw. plastic material, for. instance cellulose acetate, as in the usual granular form (P in Fig. d). to the insideof the shell l5 before the'reinforce'bar. and butt piece areVV attached thereto. In order to compensate for the.-

difference inyolume between the plastic in such granular form` and the solidified plastic (P, Fig. 5). I. may temporarily expand the shellV as by introducing compressed. air through the bore 'I andcorninunicating. small lateral passages 9 so thatthe'shell. I is blown up and bears to the iinally.- formed shelly somewhat the relationship exhibited by comparison of Figs. 4 and 5. The shell. could,.instead be pressed originally into the blownlup shape-shown by Fig` 4 andlater con tracted between: suitable dies,

Fig. 4, shows the shell I5 between two heated dies-Man di which are complementary in that onedie, namely. Allis conligured to form the shell section I6 intoproper propeller camber surfacev shape.v and the other die, 4|-, to form the shell I1 intolproper thrust surface shape. As the two dies 45t and. 4I are brought together suflicient heat. is. transferred to thethermoplastic. stock throughv the. shell walls to melt the stock and thereupon. nal: pressure is brought against the opposite sides. of the shell so asto form the iinalV propeller blade shape, atypical section of whichA is indicated at-43zinvFgl 5. The. blade, of course, has the usualor suitable twist or air-screwshape not brought out. by the drawing', An important function of.. the flanges 240i the strips 22 and 2liv in .the procedure particularly brought out-by Figs. 4 and 5.- is that any tendency for the relatively expanded camber. and thrust side walls of the shells` I6 and: I'I; to separate from the plastic as byl reason.y oi. pre-expansion for charging purposesand inherentselasticity tending to retainy the shell sectionsinexpanded condition is fully overcome by theinterlocking of the flanges with` the solidifiedplastic.

In. the case of using the.v preferredl plasticand method.of.-. introducing itt into the-shell I5,l as

above described, said shell, preferably, is charged with the proper amount of granular plastic material before the butt piece I is fastened to the shell as by brazing the flange 39 of the tube 38 (Fig. l) into place against the butt piece.

The joints between the shell sections could be at other regions than as shown in Figs. 2 to 5. The illustrated forms of shells I6 and I'I according to those figures are preferred because the shell sections have less drawing depth and are therefore less likely to wrinkle during the forming operation than if made to constitute fore and aft shell sections of the blade armor (cf. Fig. 8, described below). However, in many cases, the deep drawing such as would seem to be necessary by an arrangement according to Fig. 8 is actually a folding operation on the sheet stock over the principal areas of the sheet.

The manner of making the shells II' and I8 according t Fig. 8 so as to constitute a complete blade armor or shell I has a special advantage which compensates in part for the deep drawing or relatively diflicult forming operations in that the leading and trailing edge portions of the blade are jointless and lin that the special side wall anchor strips such as 22 and 23 are rendered unnecessary because strips such as I8, used to increase the metal stock thickness for welding purposes (or inturned anges such as illustrated at 22', Fig. 8, can function fully not only to reinforce the welded or brazed joints through interlocking with the plastic but also in effecting' a solid structure by holding the two, main side walls of the armor shell in xed relationship to each othei' through the intermediary of the solidified plastic P' when included as herein described.

A variation in essentially the method of incorporating the metal and plastic parts with each other according to Figs. 4 and 5, is illustrated by Figs. 6 and 7 wherein, instead of expanding the volumetric capacity of the pre-formed metal shell as by relative expansion of main side wall portions of the shell prior to filling the shell with raw plastic, e. g. in granular form, a different (effective) wall of the shell is initially placed in relatively expanded position with respect to the remainder of the shell, which wall is later moved to a different and nal position reducing the volumetric capacity of the hollow Wall or shell structure as a whole to correspond with the volume of the charge of plastic when solidified or cured. IThus in lieu of so making the shell I5 that the sheet metal portions may be contracted in volume as necessary to enable the plastic to fill the effective mold cavity supplied by the shell, I may make the two shell sections I6 and Il in final propeller blade shape and size and secured together and to the butt piece prior to introducing the reinforce bar into final position, and the reinforce bar becomes the effective wall of the shell which is moved to reduce the volume.

In Figs. 6 and 7 the sheet or plate 5D, which is of the same general character as the plate I0, is provided with oppositely extending lugs or tongues 5I and 52 in pairs such that terminal portions of the tongues can make contact with respective opposite walls of the shell I5 (see Fig. 7) and hold the plate 5G substantially in the desired position, for example, midway between the shell sections I5 and I 'I by yielding Contact of the tongues therewith until the plastic is cured or solidified. The reinforce bar 55, shown as separate from the butt piece I and insertable thereinto through a close fitting bore 56, can

be placed into position with a central slot 5T of the reinforce bar closely embracing the opposite sides of the sheet or plate 5B. When the reinforce bar 55 is finally moved inwardly through the bore 55 to fixed position as shown in Fig. 7 the entire space Within the shell not otherwise occupied is filled with the plastic.

The arrangement just described contemplates filling the completed shell with raw plastic stock as in Ygranular form through the bore 56 of the butt piece I, then treating the plastic until, as by application of heat to the shell walls by hot die surfaces in face to face contact with the shell, the plastic is capable of molding flow and finally inserting the reinforce bar 55 into final position by sliding engagement of a head portion 57 of the reinforce bar with the bore 56 of the butt piece. Said operation of inserting the reinforce 55 may be done in a press as by a plunger 58, Fig. 6, while the shell is supported between suitable dies or shape-maintaining means.

In the nished blade the plate 50 and reinforce bar 55 may be locked together as by a pin or plurality of pins 59 passed through at least one wall of the shell I5 through aligned openings in the reinforce bar and plate 50 as shown in Fig. 7. Spring pawl forming tongues on the plate 50 (not sho-wn) arranged to abut ratchet shoulders on the reinforce bar 55 could be used instead tolock the bar and plate 5I] together. Also the butt piece and reinforce bar may be finally pinned or otherwise secured together as at 60.

For illustrative emphasis the raw plastic material has been omitted from Fig, 6; but it is assumed that the proper amount of plastic has been introduced at the stage illustrated to cause complete lling of the shell upon movement of the bar 5 to final position and curing or solidication of the plastic and interlocking of all parts of the blade through the medium of the solidified plastic as previously described.

It will be apparent from the disclosure hereof that the present invention overcomes a problem which is generally accepted as an unavoidable disadvantage in the process of injection molding of plastic materials. A limitation in the use of the cellulose acetates and other thermoplastic materials has been the inability to form large pieces particularly if long and irregular recesses must be filled. The disadvantage comes about because it is frequently impossiblel to control the direction of flow of the plastic, and two or several streams of the plastic come together and form what is known as weld joint effects inherently weakening the molding when the joints are irn-l perfect. In the present procedure perfect integral plastic blade bodies are formed regardless of size since the raw plastic stock (e. g. loose granules) can easily reach all outlying parts of the mold (shell) before any heat or pressure is applied. A further advantage is that with the present procedure there is no tendency for the finally applied pressure to displace any of the core parts, for instance, the sheet I0 (or 55) or central reinforce 5 (or 55) out of position due to unequal flow of different stream portions of the plastic material and partial solidification in transit. The plastic portion of the blade, in other words, is certain to be integral without weld joint effects and such inherent weaknesses as discussed above. A general distinction apart from inherent organic plastic properties from certain previously proposed methods of making composite metallic and organic plastic propeller blades is that in the case of the present procedure the plastic material shrinks slightly as it solidifles from molten or plastic state and shrinks in volume considerably from the state in which it exists as raw plastic stock if granular. Therefore, no expansion joints or their equivalent are necessary such as are required if condensation products (e. g. phenol resin and allied plastics) are cured in a pre-formed metal shell.

Iclaim:

1. A propeller blade comprising in combination, cooperating separate shell sections having abutting edges joined together to unite said sections to form blade surfaces, inner reinforcing flanges along the edges of each shell section, and a ller formed by an organic plastic material constituting the body portion of the propeller, filling the shell and enclosing said reinforcing flanges so as to lock said abutting edges together.

2. A propeller blade comprising in combination, cooperating separate shell sections having abutting edges joined together tounite said sections to form blade surfaces, tapered reinforcing flanges along the edges of each shell section extending inwardly therefrom to provide a reentrant angle extending along the inner faces of said sections adjacent said edges, and a` plastic ller constituting the body portion of the propeller lling the shell and the area of said reentrant angles and enclosing said reinforcing flanges to lock said edges together.

3. A propeller blade comprising in combination, cooperating separate sheet metal shell sections having abutting edges joined together to unite said sections to form blade surfaces, inturned portions of said sections forming inwardly directed flanges along the edges of each shell section to provide re-entrant angles along the inner faces of said sections, and a plastic filler constituting the body portion of the propeller lling the shell and said re-entrant angles and enclosing said inwardly directed anges to lock said shell sections together.

GORDON W. HARDY.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,158,044 Haller May 9, 1939 1,419,180 Thomson et al. June 13, 1922 1,843,886 Semmes Feb. 2, 1932 2,262,029 McKee Nov. 11, 1941 2,217,979 Booharin Oct. 15, 1940 2,269,635 Mosehauer Jan. 13, 1942 1,384,308 DeGiers July 12, 1921 1,838,674 Heath Dec, 29, 1931 2,247,558 Nichols July 1, 1941 2,266,129 Tegharty Dec, 16, 1911 2,317,963 Bashore Apr. 27, 1943 1,846,256 Havill Feb. 23, 1932 2,215,523 Haushalter Sept. 24, 1940 1,992,338 Whitworth Feb. 26, 1935 FOREIGN PATENTS Number Country Date 341,540 Italy June 30, 1936 ri60,098 France Feb. 16, 1934 551,140 Great Britain Feb. 9, 1943 227,141 Great Britain Jan, 13, 1925 124,253 Great Britain Mar. 13, 1919 

